Defective placental maturation (syn.: maturitas retarda, lack of terminal villi, retardation of the maturation of villi, arrest of the maturation of villi, placental dysmaturity, placental maturation defect, defective placental maturation) is a normally idiopathic distortion of the development of the villi, or the placental vascularization, respectively, with a latently impaired diffusion capacity of the placenta and clinically unexpected antenatal decompensation with rapidly progressive hypoxia (11, 19, 20, 21, 25).
Defective placental maturation is associated with placental restricted functional capacity and adverse perinatal fetal outcomes. An adequate capillarization is an essential factor for placental maturation and diffusing capacity.
Two main types of disturbances to placental maturation are known and these are termed delayed and accelerated maturation. Delayed maturation or villous immaturity is characterized by the deficiency of the terminal villi and limited diffusion due to a reduction in the capillary volume fraction. In 63% of the cases, an intrauterine fetal hypoxia is correlated with the villous immaturity (28). The severe form of defective placental maturation correlates with a high incidence of macrosomy (48%), intrauterine/subpartal hypoxia (38%), intrauterine death (9%) and increased neonatal mortality (5%) (1, 25).
Accelerated maturation or villous hypermaturity is characterized by a deficiency of immature intermediate villi and a predominant differentiation of terminal villi, resulting in an intensive diffusive transport efficiency. About 50% of preterm deliveries are associated with this defect of maturity (25).
Important risk factors of defective placental maturation are diabetes mellitus type 1 and type 2, gestation diabetes, adipositas, steroid therapy and viral infections of the mother, incompatibility of blood types, and prolonged gestation (11, 20, 25).
Until today, only one effective method for a prediction of the defective placental maturation or hypoxia, respectively, is available, namely the obstetrical Doppler-sonography of the umbilical arteries (7, 8, 15). Nevertheless, this method has several disadvantages:                An inhomogeneous evaluation of the results by the attending physician depending on the level of experience;        performing the method for evaluating the placental function usually only occurs in case of risk pregnancies (16, 27);        A controversial evaluation of the results in “low-risk” births at the due date and due date overruns in the context of a monitoring (26).        
The placental maturity involving the development of numerous terminal villi (capillary network) and the formation of syncytiocapillary membranes for an optimal fetomaternal and maternofetal exchange of compounds is regulated by a series of angiogenetically effective factors and their related receptors (11).
Prokineticin 1, or “endocrine gland-derived vascular endothelial growth factor”, (also designated as EG-VEGF, PROK1, PK1 or PRK1), and its receptors PKR1 and PKR2 have been described as possible diagnostic marker in the context of the diagnosis of OHSS syndrome (31). According to more recent results, the pro-angiogenic growth factor prokineticin-1 (PK1) is involved as an essential marker in the control of the angiogenesis in reproduction specific endocrinically active tissues (32, 33, 35, 36).
The placental prokineticin 1 is a water-soluble protein which both in its structure and function is related to the growth factor VEGF (30). The activity of PK1 is mediated by the receptors PKR1 and PKR2.
An other major positive regulator of placental vascularisation is the basic fibroblastic growth factor (bFGF). bFGF is a known endothelial mitogen and angiogenic factor in vitro. It is crucial for embryonic development, mesoderm activation, and differentiation of angioblasts into the mature endothelial cells (37). bFGF mRNA expression is associated with syncytiotrophoblasts and cytotrophoblasts of the first trimester human placenta. Syncytiotrophoblast, vascular endothelium and vascular smooth muscle cells express bFGF mRNA in the term placenta (38).
Shaw et al (in Shaw J L et al, Evidence of prokineticin dysregulation in fallopian tube from women with ectopic pregnancy. Fertil Steril. 2010 October; 94(5):1601-8.e1. Epub 2010 Jan. 4) describe tissue analysis from women who are not pregnant and women with ectopic pregnancy (EP) to demonstrate expression and regulation of prokineticins (PROKs) and their receptors (PROKRs) in fallopian tube (FT). Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry were used to determine FT PROK/PROKR messenger RNA (mRNA) expression and protein localization, respectively. The PROK/PROKR levels were measured in tubal explant cultures stimulated with estrogen (E) and progestogen. The FT PROK2 and PROKR1 mRNA levels were up-regulated during the P-dominant midluteal phase of the menstrual cycle. Increased PROKR1 expression was observed in tubal explant cultures treated with medroxy-progesterone acetate (MPA). The PROK and PROKR proteins were localized to the epithelium and smooth muscle layers of the FT. The PROKR1 and PROKR2 mRNA levels were lower in FT from women with EP compared with non-pregnant FT from the midluteal phase. These data suggest a potential role for PROKs in FT function.
Catalano et al. (in Catalano et al. Prokineticins: novel mediators of inflammatory and contractile pathways at parturition? Mol Hum Reprod. 2010 May; 16(5):311-9. Epub 2010 Feb. 19) describe two proteins called prokineticins and the role they may play in labour and its premature onset. Prokineticin 1 and 2 bind to two G-protein coupled receptors, called prokineticin receptor 1 and 2. Expression of the prokineticins and their receptors is elevated in the uteroplacental unit during labour and they can induce expression of a host of genes known to be important in initiating the inflammatory and contractile events of labour. Prokineticins have also been shown to directly induce contractility of smooth muscles. Analysing the promoter regions of the prokineticins and their receptors highlights their potential regulation by pathways activated by infectious agents. They propose that infection can result in premature activation of prokineticin expression and signalling in the uteroplacental unit and this initiates a premature inflammatory and contractile cascade leading to preterm birth. Antagonism of prokineticin action may provide a suitable therapy for preterm labour that targets both inflammation and contractile pathways.
Hoffmann et al. (in Hoffmann et al. Expression and oxygen regulation of endocrine gland-derived vascular endothelial growth factor/prokineticin-1 and its receptors in human placenta during early pregnancy. Endocrinology. 2006 April; 147(4):1675-84. Epub 2005 Dec. 29) describe that a new angiogenic factor, endocrine gland-derived VEGF (EG-VEGF), also known as prokineticin 1 (PK1), has been identified, and its expression was shown to be restricted to endocrine glands, including the placenta. In this study they investigated the pattern of expression of EG-VEGF, its related factor Bv8/PK2, and their common receptors, PKR1 and PKR2, in human placenta during the first trimester of pregnancy. In isolated trophoblast cells (TCs), PKR1 mRNA is about 80 times more abundant than PKR2 mRNA. Both EG-VEGF and PKR1 mRNAs appear to be regulated by hypoxia. These findings suggest that EG-VEGF has a direct effect on TCs via its receptor PKR1 and is likely to play an important role in human placentation.
Recently, a diagnostic kit for the ELISA-prokineticin 1-diagnosis became commercially available.
The obstetrical Doppler-sonography can identify presymptomatic fetal moments of danger that are related to the vascularization of the placenta or defective placental maturation, respectively (5, 7, 8, 17). The high-risk group of pregnant subjects experiences a decrease of the perinatal mortality by 38-50%, without an increased rate of intervention.
Therefore, until now there are no reliable diagnostic methods in the prenatal care, and no laboratory markers for detecting the risks of placental hypoxia, in particular in pregnant women that are regarded as belonging to the “low-risk”-group (4, 20).
It is therefore an object of the present invention to provide such a diagnostic method for being able to make an early and reliable statement about a latently impaired diffusion capacity of the placenta or a functionally inadequate deficient fetal vasculature of the placenta in a defective placental maturation. Additional objects and aspects can be derived from reading the following description of the invention.
According to a first aspect of the present invention, this object is solved by a method for detecting a placental dysmaturity, wherein said method comprises determining the amount and/or expression and/or protein structure (polymorphism) of prokineticin 1 and/or its receptor PKR1 and/or PKR2 in a biological sample from a pregnant subject to be examined, and/or from a pregnancy (e.g. placenta, amniotic fluid, fetus). A reduced amount and/or expression and/or polymorphisms of prokineticin 1 and/or its receptor PKR1 and/or PKR2 in the sample as examined indicates an insufficiently developed fetal vasculature (organ-specific hypocapillarization) of the placental villi in the sense of a defective fetoplacental maturation (limited diffusion capacity). Thereby, the sample to be examined can either be compared with an autologous sample (e.g. taken earlier) or a sample from a healthy pregnant subject (or by means of a reference value as determined with healthy pregnant subjects). Healthy pregnant subject shall mean a pregnant subject having an appropriate placental maturity at the given point in time.
Preferred is a method for detecting a clinically latent placental insufficiency according to the present invention, wherein furthermore the ratio of the amount and/or expression of prokineticin 1 and bFGF is determined, and wherein a ratio based on bFGF>PK1 indicates a placental immaturity (organ-specific hypocapillarization), and a ratio based on bFGF<PK1 indicates a placental hypermaturity (organ-specific hypercapillarization).
The subject is a mammalian subject, such as, for example, a mouse, rat, monkey or human, and preferably is a human female subject.
The present invention thus solves the problem of an early diagnosis of the placental insufficiency, defective fetoplacental maturation, and possible prophylaxis and therapy of intrauterine hypoxia/asphyxia in the late pregnancy at the due date, and during prolonged gestation.
A reduced amount and/or expression of prokineticin 1 and/or its receptor PKR1 and/or PKR2 in the biological sample indicates an insufficiently developed fetal vasculature (organ-specific hypocapillarization), of the placental villi in the sense of a fetoplacental dysmaturity with an associated increased higher risk of an intrauterine, in particular antepartal, hypoxia. The results as presented particularly show the significant and dramatic reduction of the expression of prokineticin 1 (EG-VEGF; PK1) and its receptor PKR2 in the immature placentas exhibiting the severe form of antenatal fetal hypoxia.
The present invention particularly differs from the state from the art in that the amount and/or expression of PK1, PKR2, bFGF/PK1 in samples derived from the mother indicate adaptation disorders of the fetus (newborn)(the placenta is an fetal organ). Furthermore, the amount and/or expression of placental PK1, PKR2, and/or bFGF/PK1 in samples from the mother indicate a clinically latent disorder of the placental development of the placenta (dysmaturity), fetoplacental organ-specific hypocapillarization and reduction of the diffusion capacity of the placenta, with a fetal risk, fetal misregulation, fetal adaptation-disorders, fetal immaturity, aberrant fetal programming in the late pregnancy in “clinically healthy” pregnancies. Also, placental PK1 and PKR2 in samples of the mother in the late pregnancy are indicative for the placental development of the fetal organ specific capillaries, the diffusion capacity of the placenta and maturation of the adaptation processes of the child (maturation and activation of the fetal stress-axis, fetal hematopoiesis and “postnatal” vasculogenesis. bFGF indicates the development of the placental blood vessels of perfusion type and growth potential of the placenta and the child.
Finally, the quotient of bFGF/PK1 (perfusion capacity/diffusion capacity) was found to be optimal for the functional analysis of the placenta. bFGF/PK1 shows the balance between growth (bFGF) and maturation (PK1). Placental PK1 and bFGF pathogenetically reflect the activation of the fetal stress-axis, of the vasculogenesis from “postnatal” type and the adaptation fetoplacental. Intrauterine development of metabolically active fetal capillaries (PKR2) can determine the degree of metabolic processes in postnatal period (“fetal programming”).
Preferred is a method according to the present invention, wherein the biological sample is a body fluid sample, such as, for example, amniotic fluid, blood, serum, saliva, urine or vaginal fluid, or a solid sample, such as, for example a tissue sample, such as, for example, a placental tissue sample. The sample can be a freshly taken sample or a conserved (e.g. frozen) or prepared (e.g. tissue section) sample.
Further preferred is a method according to the present invention, wherein the pregnant subject to be examined exhibits factors for a risk pregnancy, such as, for example, diabetes type I and type II, gestation diabetes, adipositas, prolonged gestation, endocrine disease, Rhesus- or blood type incompatibility, in vitro fertilization, progressed age, steroid therapy and/or nicotine abuse (e.g. smoking).
In general, in the context of the present invention every method for determining the amount and/or the concentration is suitable that can be applied to the respective sample. Preferably, such a method comprises PCR, real time PCR (rtPCR), quantitative PCR (qPCR), ELISA, other antibody detection methods, chromatographies, centrifugation, sequencing, mutation analysis or polymorphism-analyses (34) and/or an mRNA-detection method. Polymorphisms are described, for example, in Su et al. (Su M T, Lin S H, Lee I W, Chen Y C, Hsu C C, Pan H A, Kuo P L. Polymorphisms of endocrine gland-derived vascular endothelial growth factor gene and its receptor genes are associated with recurrent pregnancy loss. Hum Reprod. 2010 November; 25(11):2923-30. Epub 2010 Sep. 16), or referred to in the databases as rs7514102, rs59863268, and rs17628376.
According to the invention, also genetic abnormalities or pathological polymorphisms of the gene for prokineticin 1 and/or the gene for PKR1 or PKR2 can be determined in the sample of the pregnant subject (see e.g. Su M T, et al. Polymorphisms of endocrine gland-derived vascular endothelial growth factor gene and its receptor genes are associated with recurrent pregnancy loss. Hum Reprod. 2010 November; 25(11):2923-30. Epub 2010 Sep. 16). Thus, a change of the amount and/or the concentration of prokineticin 1 and/or its receptor PKR1 and/or PKR2 is identified “indirectly”, using their genetic basis. Thereby, a genetic abnormality of the gene prokineticin 1 and/or the gene for PKR1 or PKR2 indicates a distorted regulation of the fetoplacental angiogenesis with an insufficiently developed fetal vasculature of the placental villi in the sense of a fetoplacental dysmaturity with an associated higher risk for an intrauterine, in particular antepartal, hypoxia.
As a further step (or steps), the method for detecting a fetoplacental dysmaturity of the present invention can comprise a further detection using data derived from a Doppler-sonography. The Doppler-sonography can either be performed for a confirmation and/or several times in parallel (as a supplement) or extension for the method according to the present invention. Regarding this, see also further below.
As mentioned above, a reduced amount and/or concentration of prokineticin 1 and/or its receptor PKR1 and/or PKR2 in the sample indicates an insufficiently developed fetal vasculature of the placental villi in the sense of a placental insufficiency. The ratio of the amount and/or expression of prokineticin 1 and bFGF is also indicative of a placental insufficiency. Thus, particularly preferred is a method according to the present invention, wherein the amount and/or the concentration of the marker as determined in the sample is reduced by at least a factor of 2, preferably a factor of 4, when compared with a sample from a healthy pregnant subject.
Further preferred is a method according to the present invention, wherein the pregnant subject to be examined stems from a non-preselected group of pregnant subjects. This means that for the first time the method of the invention makes it possible to perform serial examinations. This will allow for the identification of yet unrecognized diseases and thus ultimately makes a prophylaxis of intrauterine hypoxia/asphyxia at the due date and in prolonged gestation possible.
A further aspect of the present invention then relates to a method for monitoring a risk-pregnancy, comprising a method according to the present invention as described above and the step (or steps) of an additional monitoring of the pregnant subject by means of data derived from a Doppler-sonography. Thus, here advantageously the combination of the present invention with known methods is used.
A further aspect of the present invention then relates to a method for determining the risk of an intrauterine, in particular antepartal, hypoxia in a pregnant subject, comprising detecting a placental insufficiency according to a method according to the present invention as described above and a subsequent determination of the risk using the data as obtained, such as, for example, the bFGF/PK1-ratio. In case of a placental insufficiency as found, the risk is increased.
The method can furthermore comprise an identification of the risk of a recurrence of a fetal hypoxia in the next pregnancy/pregnancies in case of a condition following intrauterine death which is also based on the method as described here, and the use of data as accordingly obtained. This represents a preferred example of preventive diagnostic on the basis of the invention.
A still further aspect of the present then relates to a method for determining a risk-adapted due date in a pregnant subject, comprising a method according to the present invention as described above and determining of a minimal-risk due date in a pregnant subject that was detected to have a latent placental insufficiency in form of a placental dysmaturity. Preferred is such a method according to the present invention, wherein in case of an identified additional risk for a placental insufficiency the due-date is set beginning from the 35th week of pregnancy. Thereby, after this point in time the risk for a hypoxia can be markedly reduced.
A further aspect of the present invention then relates to a method for treating a placental insufficiency involving a latent placental insufficiency, comprising a method according to the present invention as described above and a treatment of a placental dysmaturity as detected by means of suitable medicaments, e.g. hormones or insulin or heparin therapy. The outcome-dependent stimulation of PKS and bFGF may be a useful strategy for therapeutic fetoplacental neovascularization. This aspect relates to the direct treatment of the placental dysmaturity on the basis of the diagnosis by the attending physician.
A still further aspect of the present invention then relates to a method for treating a risk-pregnancy, comprising a method according to the present invention as described above and an additional treatment of the underlying disease by means of suitable medicaments. By “underlying disease” the secondary disease or condition of the pregnant subject shall be understood, such as, for example diabetes type I and type II, gestation diabetes, adipositas, prolonged gestation, condition following intrauterine death, endocrine disease, Rhesus- or blood type incompatibility, in vitro fertilization, progressed age, steroid therapy and/or nicotine abuse (e.g. smoking). Preferably, the disease is selected from gestation diabetes or blood type incompatibility. Of course, also mixed direct and indirect treatment schemes are contemplated by the invention.
The treatment methods according to the present invention as a further step (or steps) can comprise a further detection using data obtained from a Doppler-sonography. The Doppler-sonography can either be performed for a confirmation and/or can be performed one or several times in parallel (as a supplement) or as an extension for the method according to the present invention.
A still further aspect of the present invention then relates to a method for monitoring the medicamentous therapy of a risk-pregnancy, comprising performing the method according to the present invention as described above on a sample of a pregnant subject which undergoes a respective medicamentous therapy. This “monitoring” of the development of the fetal placental vessels can be performed, for example, in several temporally spaced samples as a continuous monitoring.
The method according to the invention for monitoring the medicamentous therapy of the risk-pregnancy as a further step (or steps) can comprise an additional detection using data from a Doppler-sonography. The Doppler-sonography can either be performed for a confirmation and/or can be performed one or several times in parallel (as a supplement) or as an extension for the method according to the present invention.
A still further aspect of the present invention then relates to the use of a diagnostic kit for the prokineticin 1-diagnosis, optionally together with bFGF, and/or the diagnosis of the receptor PKR1 and/or PKR2 in a sample in a method according to the present invention. The kit can contain respective materials for e.g. ELISA or oligonucleotides for the PCR, together with buffers and corresponding other auxiliary agents, as well as manuals and evaluation documentation. Preferred is a point of care (POC)-test kit.
A further aspect of the present invention then relates to a method for identifying a compound that influences placental dysmaturity in a pregnant subject, comprising performing a method according to the present invention as described here on a sample that was obtained from said pregnant subject and/or the pregnancy before the administration of the compound to be tested, and comparing of said sample with a sample that was obtained from said pregnant subject and/or the pregnancy after the administration of the compound to be tested, wherein a change of the amount and/or the expression of prokineticin 1, optionally together with a change of the amount and/or the expression of bFGF, and/or the receptor PKR1 and/or PKR2 indicates a compound which influences placental dysmaturity in a pregnant subject.
Preferred is a method for identifying a compound that influences placental dysmaturity in a pregnant subject according to the present invention, wherein the placental dysmaturity is influenced through influencing/modifying of the activity of prokineticin 1, optionally together with a change of the amount and/or the expression of bFGF, and/or the receptor PKR1 and/or PKR2. This activity of prokineticin 1, bFGF, and/or the receptor PKR1 and/or PKR2 can be the biological and/or biochemical activity, or the expression of the gene/s that encode for prokineticin 1 and/or its receptor PKR1 and/or PKR2. The compound can be an agonist or antagonist of the activity. Preferred is an agonist that increases the activity of prokineticin 1 and/or its receptor PKR1 and/or PKR2, and decreases the activity of bFGF.
The term “antagonist” is used herein in its broadest sense and includes every molecule that partially or completely blocks, inhibits or neutralizes the biological and/or biochemical activity of the prokineticin 1 and/or its receptor PKR1 and/or PKR2, or bFGF. In a similar manner, also the term “agonist” is used herein in its broadest sense and includes every molecule that mimics or promotes the biological and/or biochemical activity of the prokineticin 1 and/or its receptor PKR1 and/or PKR2, or bFGF. Suitable agonists or antagonist-molecules include specific agonist- or antagonist-antibodies or antibody-fragments, fragments of prokineticin 1 and/or its receptor PKR1 and/or PKR2 or bFGF, antisense oligonucleotides, small organic molecules, etc. Methods for identifying agonists or antagonists of prokineticin 1 and/or its receptor PKR1 and/or PKR2 or bFGF can comprise a contacting of the polypeptide for prokineticin 1 and/or its receptor PKR1 and/or PKR2 or bFGF with a candidate-agonist- or antagonist-molecule, and measuring and/or detecting a change in one or several biological activities, such as, for example, the maturity of villi.
Preferred is a method for identifying a compound that influences placental dysmaturity in a pregnant subject according to the present invention, wherein said measuring and/or detecting the change in one or several biological activities by means of expression comprises the use of an antibody against prokineticin 1 and/or its receptor PKR1 and/or PKR2 or bFGF, and/or an RT-PCR and/or other tests, as described above for the diagnosis.
The present invention solves the problem of a particularly early diagnosis of latent placental insufficiency in pathological placental dysmaturity and the possible prophylaxis of intrauterine hypoxia/asphyxia at the due date and upon prolonged gestation.
A reduced amount and/or concentration of prokineticin 1 and/or its receptor PKR1 and/or PKR2 indicate an insufficiently developed fetal vasculature (hypocapillarization) of the placental villi in the sense of a placental dysmaturity with an increased fetal risk of an intrauterine, in particular antepartal, hypoxia.
The present invention furthermore allows for
a) establishing of new screening methods for an early identification of a risk of placental hypoxia—also in comparison to other methods—in unselected, that is not preselected, groups of pregnant subjects,
b) the safe and early diagnosis of the latent placental insufficiency or placental dysmaturity using quantitative methods, as a support for the risk-adapted induction of birth or selection, also with prolonged gestation (23),
c) the monitoring of preventive strategies and the control of the progression of the therapy in risk pregnancies, in particular in diabetes mellitus, gestation diabetes, other endocrine maternal diseases, adipositas, prolonged gestation, Rhesus- or blood group incompatibility, in vitro fertilization, progressed age, steroid therapy and/or nicotine abuse, andd) new specific treatment concepts for improving the fetoplacental function and optimal extension/progression of the pregnancy.
Thus, the invention for the first time, also in the context of a screening of patients, allows the simple, safe and early identification of pregnant women that during pregnancy are at a high risk to develop a “respiratory” insufficiency of the placenta with hypoxic damage to the unborn child.
The introduction of a test for prokineticin 1 and/or its receptor PKR1 and/or PKR2 for the routine-diagnosis leads to new possibilities in the prophylaxis of fetal hypoxia/asphyxia or emergency caesarean section with a decrease of the perinatal mortality and morbidity as well as an avoidance of irreversible damage to the organs of the children, in particular brain damage (24).
On the basis of the detection according to the present invention, the physician is thus able to:                Early detect pregnant subjects with a high risk of a later intrauterine hypoxia, even before additional symptoms occur;        monitor those pregnancies that are fraught with a risk more closely (e.g. by Doppler-sonography) in order to achieve a safe result for both mother and child;        initiate respective treatment options (e.g. in case of gestation diabetes, blood type incompatibility);        control the effectiveness of the medicamentous therapy (e.g. insulin therapy), and        Optionally, set a risk-adapted date of delivery (if additional risks for a placental insufficiency are present, a termination of the pregnancy already after the 37th week of pregnancy might have advantages for both mother and child).        
Because of the large clinical importance of the antenatal intrauterine hypoxia, the method according to the present invention will improve the health care for pregnant women, improve the clinical prevention of risk-patients as identified, and also will lower costs because of a rationalization of the prevention for pregnant women, and a reduction of the substantial follow-up costs in case of children that were harmed.
The following Table 1 further summarizes the differences and advantages of the present invention, compared to the state of the art:
ReferenceHoffmannInventionShaw 2010Catalano 20102006Aim of screeningClinically latentTubarPremature labourPreeclampsiaforms ofgravidity(premature birth)placentalinsufficiencyincluding therisk of anantenatalHypoxia of thechildRisk stratificationLow on risk—heterogeneousRisk pregnancy(prevention)Primary diseaseFetoplacentalMaternalMaterno-Materno-placentaldiseasediseaseplacental diseasediseasePredominance ofYesNoNoNofetal disordersPredominance ofNoYesYesYesmaternal disordersClinical symptomsWithoutpresentpresentpresentduring pregnancysymptomsWeek of pregnancyIII TrimesterI TrimesterII-III TrimesterII-III TrimesterAntenatal 35-43Early20-35 WOP20-35 WOPWOPgravidityPlacentalChronically-Non-viableacuteChronic (not latent)insufficiencylatent, terminallypregnancyacuteDuration of theMonths (noDaysDaysMonths (Screening-placentalscreening-methods available)insufficiencymethods)PredominantFetoplacentalTuba uterinaMusculature ofUteroplacentalpathologicalVasculature(mother)the uterusvasculaturelocalisation(fetal side)(maternal side)(maternal side)Genesis of the PK1-FetoplacentalmaternalMaternoplacentalMaternoplacentalChangesPKs-ReceptorsPKR2PKR1EffectReduction of theIncreasedIncreasedObliteration of thefetal capillariescontractivitycontractivity ofspiral arteriesand limitation ofof thethe musculature(maternal)the diffusionmusculature(Uterus)capacity of the(Tube)placentaPrimary type ofPostplacental—PreplacentalPreplacental (Uterus)hypoxia(Child)(Uterus)
The results of the inventors show that PK1 and PKR2 are essential for the regulation of terminal villi differentiation. Observed was a significantly decreased expression of PK1 and PKR2 but not PKR1 in the placentas with terminal villous deficiency in comparison to the control group. In the placentas with a predominant terminal villous differentiation, PK1 and PKR2 expression was highly elevated compared to the normal placentas. The terminal villi development was reflected by the aberration of the organ-specific capillarization and diffusion capacity. Thus, the decrease of PK1/PKR2 signaling in the placenta with delayed maturation is associated with terminal villous deficiency, hypocapillarization and limited diffusion capacity. Increased PK1/PKR2 signaling in the placentae with accelerated maturation was associated with a predominance terminal villous differentiation, hypercapillarization and improved placental diffusion.
In the placenta with a defect in the maturation and aberrant PK1/PKR2 expression there seems to be an altered transfer of steroid hormones and their precursors into maternal and fetal blood. This may be the reason for the deviations of the maturation and activation of fetal hypothalamic-pituitary/sympaticus-adrenal axis, of the beginning of the fetal “postnatal” type of vasculogenesis, of the fetal steroids synthesis and, as a result, abnormalities of the fetus and placenta maturation. This hypothesis is consistent with the results of stereological and electron microscopy studies on human placental villi.
The inventors have also determined an inverse relationship between placental capillarization and the level of the bFGF expression. Increased bFGF expression was revealed in the placentae with terminal villous deficiency and hypocapillarization. Arany et al. (1998) also observed elevated bFGF expression in the diabetic placentae caused by increased expression in syncytiotrophoblast.
In contrast, bFGF expression was decreased in the accelerated matured placentas with enlarged terminal villi differentiation and placental hypercapillarization. A direct correlation was observed between bFGF expression and immature intermediate villi differentiation and formation of resistance vessels. Thus, intermediate villous deficiency with a decrease in placental resistance vessels, and limited placental perfusion is associated with the decrease of placental bFGF signaling.
It was further found that the VEGF and PlGF expression in the placenta with delayed maturation did not differ from the control group. PlGF expression in the placenta with accelerated maturation is also comparable with the normal control tissue, but VEGF expression is decreased and this may be the cause of the decrease of the branching angiogenesis. The results support the fact that hypoxia is not a key pathogenic factor of the placental maturity disruption.
Importantly, the inventors have also shown that antenatal placental insufficiency associated with defective maturation is accompanied by an imbalance of bFGF/PK1-expression. bFGF-hyperexpression (bFGF>PK1) results in placental immaturity with a predominance of immature villi, hypocapillarization, and structurally and functionally limited diffusion. PK1-hyperexpression (bFGF<PK1) reflects placental hypermaturity with a predominance of terminal villi, hypercapillarization, and limited perfusion. The bFGF/PK1-ratio is therefore a marker of the latent clinical restrictions of the placental function causing a potential risk resulting in fetal hypoxia.